Volume control system



Jan. 10, 1933. E. R. HENTSCHEL VOLUME CONTROL SYSTEM Filed Aug. 9, 1930 J2EE?"- INVENTOR.

T tMe/ar 3Tb BY 6 ATTORNEY Patented Jan. 10, 1933 UNITED STATES PATENT OFFICE ERNEST R. HENTSOHEL, OF WASHINGTON, DISTRICT OF COLUMBIA; JOH'N OLSON, AD-

MINISTRATOR OF SAID IFJRNEST R. HENTSCHEL, DECEASED, ASSIGNOR TO WIRED RADIO, INCL, OF NEW YORK, N. "55., A CORPORATION OF DELAWARE VOLUME CONTROL SYSTEM Application filed August 9, 1930. Serial N0. 474,208.

My invention relates broadly to radio receiving systems and more particularly to a volume control circuit for radio receiving systems for maintaining the volume of reproduced sound at the receiver substantially uniform regardless of the effects of fading.

One of the objects of my invention is to pro vide a circuit arrangement for radio receiv er including a volume control circuit of high sensitivity for maintaining the volume of reproduced sound substantially uniform in dependently of fading effects.

Another object of my invention is to provide a volume control circuit for radio receivers in which an increase in the amplitude of received signaling energy tends to increase the impedance in the radio frequency energy collecting circuit for automatically maintaining a substantially constant level of reproduced sound at the receiver.

Still another object of my invention is to provide an automatic volume control circuit for radio receivers wherein an electrostatic device may be controlled by increase in ampli tude of the current in the sound reproducing circuit for increasing the impedance of the radio frequency energy pick-up circuit for maintaining the volume of reproduced sound substantially uniform.

A further object of my invention is to provide an arrangement of electrostatic control device adapted to modify the characteristics of the receiving circuit in a signal receiving system according to increase in amplitude of the current through the sound reproducingcircuit due to such. causes as the fading phenomena.

Other and further objects of my invention reside in a circuit arrangement whereby the operation of an electrostatic device may be controlled according to the amplitude of the current in the sound reproducer circuit of a radio receiver for detuning or increasing the impedance of the circuits connected with the receiving circuit as more fully set forth in the specification hereinafter following by reference to the accompanying drawing, in which:

Figure 1 diagrammatically illustrates a radio receiving circuit embodying the principles of my invention; and Fig. 2 shows a modified circuit arrangement for the electrostatic control system of my invention.

In radio broadcast receivers the quality of sound reproduction is often impaired by the tendency of the reproduced sound to sudden ly increase in volume due to such causes as the fading phenomena. Fading effects produce an undesirable condition in the circuits of a broadcast receiver in that the current amplitude in the sound reproducing circuit tends to increase beyond that value at which the reproduction from the sound reproducer is obtained. My invention provides means directly controlled from the sound reproducing circuit for electrostatically introducing a sufficient impedance in the radio frequency energy pick-up circuit or sufliciently detuning the circuits of the receiver to compensate for the tendency of the sound reproducer to chat ter or distort under the effects of increased signal strength. I provide an audio frequency coupling transformer having its primary Winding disposed. in series with the output circuit of the last stage of power amplification and in circuit with the sound reproducer. The secondary of this transformer has its terminals connected to the terminals of an clectroscopic device. The electroscopic device is suitably arranged in circuit with the radio frequency energy pick-up circuit or in circuit with a portion of the tuned circuit of the receiver in such manner that a sufficient impedance is introduced into the radio fre quency energy pick-up circuit or the circuits of the receiver are sufliciently detuned to enable the volume of reproduced sound to be maintained substantially constant under the effects of fading or other phenomena.

Referring to the drawing in detail, reference character 1 designates an antenna con nected to ground 2 through the primary wind- 3 of coupling transformer 4. The secon dary winding 5 of coupling transformer 4 is tuned by condenser 6 and connects to the input system of a radio frequency amplifier which for the purpose of illustrating my invention has been designated by a single stage including an electron. tube 7 The output circuit of electron tube 7 connects through coupling transformer 8 with the input circuit of the detector 9. The input circuit of detector 9 is tuned by suitable condenser illustrated at 10. The output circuit of detector 9 connects through audio frequency coupling transformer 11 with the audio frequency or power amplifier which for the purposes of illustrating my invention has been illustrated bythe single stage 12. of the power amplifier 12 connects through audio frequency transformer 14 with the source of plate potential which is obtained from a tap 15 on potentiometer 16 where the potentiometer 16 is energized from a source of rectified alternating current. The power circuits include the power transformer 17 having a secondary winding connected to rectifier circuit 18 and filter circuit 19 for deliverin filtered rectified alternating current to the potentiometer; The cathode circuits for the several tubes are energized from secondary winding 20 of the power transformer as shown. The audio frequency transformer it in the output of the final stage of power'amp'lification includes primary winding 21 and secondary winding 22. Leads 23 eXtend from secondary winding 22 to the terminals of an electroscopic device contained within vessel 24. Two fixed electrodes are arranged within vessel 24 as shown at 25 and 26. The electrodes 25 and 26 are disposed in fixed angular relationone with respect to the other as illustrated and each face of the electrodes 25 and 26 are covered with a sheet of insulation shown at 251 and 26a. A movable electrode of light leaf-like conductive material is shown at 27, pivotally mounted at 28 and normally urged by spiral spring 29 to the position illus trated forming a capacitative relationship between plate .27 and rigid plate 26. The plate 27 and plate 26 are connected in the antenna circuit in series relation. A choke coil connects in shunt with respect to plates 27 and 26. The radio frequency energy is therefore forced to take a path capacitatively across plates '27 and 26 in series with the antenna-circuit. A. maximum amount of energy flows in the antenna circuit where the electroscopic device assumes the position illustrated in Figs. 1 and 2, that is where the impedance of a device to radio frequency currents is relatively small.

The audio frequency current supplied over the circuit 28 passes through choke coil 31 to electrode 25 at one side of the circuit and at the other side of the circuit charges are impressed upon electrode 26. The choke coil 30 while offering large impedance to radio frequency currents in the antenna path, offers practically no impedance to audio frequencycurrent from the circuit 23 and hence permits movable plate 27 and stationary electrode 26 to assume the'same potential as the end 22a of the secondary winding 22 while electrode 25 assumes thepotential of the end The output circuit 22?) of secondary winding 22. Charges of one potential are therefore impressed upon electrode 25 while charges of an opposite potential are impressed upon electrodes 27 and 26. When the signal amplitude in the output circuit of power tube 12 becomes large the potential across winding 22 is large and plate 27 is repelled from electrode 26 decreasing the efiectiye capacity and increasing the impedance of the antenna circuit thus reducing the current in primary winding 3 of coupling transformer l. iflovement of plate 27 away from electrode 26 is due to a repelling action between plate 27 and electrode 26 and an attractive action between electrode 25 and plate 27.

The electroscopic device 24 may be disposed in various locations in the receiver. In Fig. 2 T have shown the electroscopic device arran ed to chan e the resonant fre uenc of the tuned circuit 56 within the radio frequency amplifier. In this arrangement plate 26 serves as an auxiliary tuning condenser connecting in parallel with main condenser 6. W hen the E. M. F. across coil '22 increases, 6

by the mass of moving plate 27 and by the friction of the pivot 28 and the tension of the light spring 29. In order that the-radio frequency current may be excluded from the transformer circuit 14: the choke coil 31 is formed of such character that while the audio frequency charges are readily passed to electrode 25 a large impedance is offered to the passage of radio frequency current. The electroscopic device is therefore actuated by electrostatic charges proportional to the amplitude of the energy passingthrough the loud speaker '13 for directly controlling the effective capacity between moving plate 27 and electrode 25 for modifying the characteristics of the receiving circuit. As soon as the effective signaling energy has been reduced by operation of the. electroscopic devices, the current in winding 22 is reduced to normal bringing about a stabilized operation of the electroscopic device.

Sufficient damping is introduced to prevent movement of plate 27 due to normal fluctuations of the signaling energy in the sound reproducer circuit. This is accomplished by filling the enclosing vessel 24 with fluid indicated at 32 so that sufiicient inertia to the movement of plate 27 is'introduced to enable the electroscopic device to respond to variations in volume of reproduced sound due to fading effects and radical changes in current in the sound reproducing circuit 13 while being non-responsiveto normal fluctua tions in amplitude in accordance with the normal reproduction of music or the articula tion of speech.

its

While I have described my invention in certain preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a signal receiving system, a radio frequency energy pick-up circuit, a receiving circuit connected with said aforesaid circuit, a sound reproducer operated by said receiving circuit, an electroscopic device having terminals thereof connected in series in said radio frequency energy pick-up circuit, and a control circuit disposed in series with said sound reproducer and connected with said electroscopic device for impressing charges upon said electroscopic device for varying the effective capacity thereof and modifying the characteristics of said radio frequency energy pick-up circuit.

2. In a signal receiving system, a radio frequency energy pick-up circuit, an amplification circuit connected with said radio frequency energy pick-up circuit, a detector circuit connected with said amplification circuit, an amplification circuit connected with said detector circuit, a sound reproducer connected with the output of said last mentioned amplification circuit, means for deriving variable electrostatic charges proportional to signal amplitude in the circuit including said sound reproducer, and an electroscopic device connected with said radio frequency energy pickup circuit and controlled by said variable charges for modifying the characteristics of said radio frequency energy pick-up circuit and correspondingly controlling the volume of reproduced sound.

3. In a signal receiving system, a radio frequency energy pickup circuit, a signal receiving circuit connected therewith, a detector connected with said signal receiving circuit, a sound reproducer connected with said detector, means for deriving variable electrostatic charges proportional to the signal amplitude in the circuit including said sound reproducer, an electroscopic device connected with said radio frequency energy pick-up circuit, means for impressing said variable charges upon said electroscopic device, for modifying the characteristics thereof according to the volume of reproduced sound for correspondingly controlling the tuning of said radio freq uency energy pick-up circuit.

4. In a signal receiving system, a radio frequency energy pick-up circuit, a signal receiving circuit connected therewith, a detector connected with said signal receiving cire cuit, a sound reproducer connected with said detector, means for deriving variable electrostatic charges proportional to the signal amplitude in the circuit including said sound reproducer, an electroscopic device comprising a pair of fixed electrodes and an interme diate movable electrode, mean s for impressing charges of one polarity upon one of said fixed electrodes and charges of the opposite polarity conjointly upon the other of said fixed electrodes and said movable electrode for effecting a displacement of said movable electrode and varying the effective capacity between said movable electrode and said last mentioned fixed electrode, and connections between said last mentioned fixed electrodes and said movable electrode with said signal receiving circuit for modifying the characteri tics thereof according to the volume of reproduced sound.

5. In a signal receiving system, a radio frequency energy pick-up circuit, a signal receiving circuit connected with said radio frequency energy pick-up circuit, a detector connected with said signal receiving circuit, a sound reproducer connected with said detector, an electroscopic device comprising a pair of fixed electrodes and an intermediate angularly shiftable electrode, one of said fixed electrodes and said intermediate shiftable electrode being connected in series with said radio frequency energy pick-up circuit for establishing a variable capacity path therein, means connected in shunt with said fixed electrode and said shiftable electrode hav ng high impedance to radio frequency current and substantially no impedance to audio frequency current, and means for deriving electrostatic charges from the circuit including said sound reproducer for impressing charges of one. polarity upon one of said fixed electrodes and charges of an opposite polarity upon the other of said fixed electrodes and through said means upon said angularly shiftable electrode, for displacing said angularly shiftable electrode and varying the electrostatic capacity with respect to the associated fixed electrode, whereby the effective ampl tude of signaling energy transferred to said s gnal receiving circuit is controlled in accordance with the volume of reproduced sound.

6. In a signal receiving system, a signal receiving circuit, a sound reproducer actuated thereby, an electroscopic device including a pair of fixed electrodes and an intermediate angularly movable electrode, connections between one of said fixed electrodes and said angularly movable electrode with said signal receiving circuit for establishing a variable capacity path therein, means for deriving variable electrostatic charges proportional to the amplitude of signal current in the circuit including said sound reproducer, and means for impressing charges of one polarity upon one of said fixed electrodes, and charges of the opposite polarity upon the other of said fixed electrodes and upon said angularly movable electrode'for controlling the effective capacity between said last named fixed electrode and said angularly movable electrode and correspondingly controlling the amplitudeof signal energy supplied to said sound reproducer.

7. In a signal receiving system, a signal receiving circuit, a sound reproducer actuated thereby, an electroscopic device including a pair of fixed electrodes and an intermediate angularly movable electrode, connections between one of said fixed electrodes and said angularly movable electrode with said signal receiving circuit for establishing a variable capacity path therein, means for deriving variable electrostatic charges proportional to the amplitude of signal current in the circuit including said sound reproducer, and means including choke coils having high impedance to radio frequency currents and low impedance to audio frequency charges for impressing charges of one polarity upon one of said fixed electrodes, and charges of the opposite polarity upon the other of said fixed electrodes and upon said angular-1y movable electrode for controlling the effective capacity between said last named fixed electrode and said angularly movable electrode and correspondingly controlling the amplitude 01" signal energy supplied to said sound reproducer.

8. In a signal receiving system, asignal receiving circuit, a. sound reproducer actuated thereby, an electroscopic device including a pair of fixed electrodes and an intermediate angularly movable electrode, connections between one of said fixed. electrodes and said angularly movable electrode with said sig nal receiving circuit for establishing a variable capacity path therein, means for deriving variable electrostatic charges proportional to the amplitude of signal current in the circuit including said sound reproducer, means for impressing charges of one polarity upon one of said fixed electrodes, and charges of the opposite polarity upon the other of said fixed electrodes and upon said angularly movable electrode for controlling the effective capacity between said last a named fixed electrode and said angularly movable electrode and correspondingly controlling the amplitude of signal energy supplied to said sound reproducer, andmeans for damping the movement of said movable electrode with respect to said fixed electrodes.

9. In a signal receiving system, a signal receiving circuit, a sound reproducer actuated thereby, an electroscopic device including a pair of fixed electrodes and an intermediate angularly movable electrode, connections be tween one of said fixed electrodes and said angularly movable electrode with said signal receiving circuit for establishing a variable capacity path therein, means for deriving variable electrostatic charges proportional to the amplitude of signal current in the circuit electrodes and upon said angularly movable v 1 electrode for controlling the effective capacity between said last named fixed electrode and said angularly movable electrode and correspondingly controlling the amplitude of signal energy supplied to said sound reproducer, and means for biasing the positionof said movable electrode with respect to said fixed electrodes. v I

- In testimony whereof I affix my signature.

ERNEST R. HENTSOHEL. 

